Matthew weakened slightly to a Category 4 major hurricane early Saturday as it barreled through the Caribbean, on target to approach Jamaica late Sunday and likely brush southeast Florida at mid-week.

En route, it also threatens Haiti, Cuba and the Bahamas into Monday.

AccuWeather Senior Meteorologist Bernie Rayno says if Matthew moves swiftly as it heads north, it has a greater chance of causing significant impact from rain, wind and flooding along along much of the Atlantic coast.

"On the other hand, if Matthew's forward speed slows, it could still have significant impact on the Atlantic coast, but in a much smaller area, when compared to a fast-moving hurricane," he says.

The center five-day forecast shows Matthew's cone — which marks its outer edges of the hurricane's probable trek northward — encompassing a slice of southeast Florida by early Wednesday.

The National Hurricane Center also warns of likely life-threatening surf and rip current conditions over a wide area from Puerto Rico to Venezuela.

As of 5 a.m ET, Matthew had maximum-sustained winds of 155 mph — just 2 mph shy of Category 5 status that it reached on Friday. Matthew threatens to deliver a powerful punch to the area into Monday, the center said. It was moving to the west at 7 mph and was located about 420 miles southeast of southeast of Kingston, Jamaica

A hurricane watch is in effect for Jamaica and a tropical storm watch has been issued for portions of Haiti.

A hurricane is classified as "major" when its sustained winds reach 111 mph. A major hurricane is a Category 3, 4 or 5 on the Saffir-Simpson Hurricane Wind Scale. It's the first major hurricane in September in the Caribbean since Felix in 2007.

Sometime on Saturday or early Sunday, Matthew should make its long-anticipated northwest or northward turn in the Caribbean Sea, weather.com reported.

In Jamaica, Prime Minister Andrew Holness said government services have been placed on high alert, according to the Jamaica Observer newspaper. Thursday, fishermen on Jamaica’s cays and banks were advised to evacuate immediately and return to the mainland.

Other small craft operators in the island’s coastal waters were also told to return to port, while those in port were advised not to venture out, the newspaper reported.

Florida Gov. Rick Scott said the state emergency operations centers were active on Friday. He said state officials will continue monitoring Matthew's path and urged residents and tourists to monitor the storm and have their emergency plan in place.

"While the National Hurricane Center's current forecast predicts Matthew traveling east of Florida, we all know that the track of these storms can quickly change," Scott said.

Whether or not impacts will be indirect from a hurricane at sea or direct from a landfall in the U.S. are still unclear, AccuWeather said.

"It is too soon to rule out possible hurricane impacts from Matthew in Florida," according to the hurricane center.

Even if Matthew turns toward the sea next week, rough surf and heavy seas would occur along the Atlantic coast.

Hurricane Matthew is the 5th hurricane and 2nd major hurricane of the 2016 Atlantic hurricane season. It's now the only hurricane or typhoon on the planet.